/* Copyright 2004, 2005, 2006 Acegi Technology Pty Limited
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.acegisecurity.intercept;

import org.acegisecurity.AccessDecisionManager;
import org.acegisecurity.AccessDeniedException;
import org.acegisecurity.AcegiMessageSource;
import org.acegisecurity.AfterInvocationManager;
import org.acegisecurity.Authentication;
import org.acegisecurity.AuthenticationCredentialsNotFoundException;
import org.acegisecurity.AuthenticationException;
import org.acegisecurity.AuthenticationManager;
import org.acegisecurity.ConfigAttribute;
import org.acegisecurity.ConfigAttributeDefinition;
import org.acegisecurity.RunAsManager;

import org.acegisecurity.context.SecurityContextHolder;

import org.acegisecurity.event.authorization.AuthenticationCredentialsNotFoundEvent;
import org.acegisecurity.event.authorization.AuthorizationFailureEvent;
import org.acegisecurity.event.authorization.AuthorizedEvent;
import org.acegisecurity.event.authorization.PublicInvocationEvent;

import org.acegisecurity.runas.NullRunAsManager;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.beans.factory.InitializingBean;

import org.springframework.context.ApplicationEvent;
import org.springframework.context.ApplicationEventPublisher;
import org.springframework.context.ApplicationEventPublisherAware;
import org.springframework.context.MessageSource;
import org.springframework.context.MessageSourceAware;
import org.springframework.context.support.MessageSourceAccessor;

import org.springframework.util.Assert;

import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

/**
 * Abstract class that implements security interception for secure objects.
 * <p>
 * The <code>AbstractSecurityInterceptor</code> will ensure the proper startup
 * configuration of the security interceptor. It will also implement the proper
 * handling of secure object invocations, being:
 * <ol>
 * <li>Obtain the {@link Authentication} object from the
 * {@link SecurityContextHolder}.</li>
 * <li>Determine if the request relates to a secured or public invocation by
 * looking up the secure object request against the
 * {@link ObjectDefinitionSource}.</li>
 * <li>For an invocation that is secured (there is a
 * <code>ConfigAttributeDefinition</code> for the secure object invocation):
 * <ol type="a">
 * <li>If either the {@link org.acegisecurity.Authentication#isAuthenticated()}
 * returns <code>false</code>, or the {@link #alwaysReauthenticate} is
 * <code>true</code>, authenticate the request against the configured
 * {@link AuthenticationManager}. When authenticated, replace the
 * <code>Authentication</code> object on the
 * <code>SecurityContextHolder</code> with the returned value.</li>
 * <li>Authorize the request against the configured
 * {@link AccessDecisionManager}.</li>
 * <li>Perform any run-as replacement via the configured {@link RunAsManager}.</li>
 * <li>Pass control back to the concrete subclass, which will actually proceed
 * with executing the object. A {@link InterceptorStatusToken} is returned so
 * that after the subclass has finished proceeding with execution of the object,
 * its finally clause can ensure the <code>AbstractSecurityInterceptor</code>
 * is re-called and tidies up correctly.</li>
 * <li>The concrete subclass will re-call the
 * <code>AbstractSecurityInterceptor</code> via the
 * {@link #afterInvocation(InterceptorStatusToken, Object)} method.</li>
 * <li>If the <code>RunAsManager</code> replaced the
 * <code>Authentication</code> object, return the
 * <code>SecurityContextHolder</code> to the object that existed after the
 * call to <code>AuthenticationManager</code>.</li>
 * <li>If an <code>AfterInvocationManager</code> is defined, invoke the
 * invocation manager and allow it to replace the object due to be returned to
 * the caller.</li>
 * </ol>
 * </li>
 * <li>For an invocation that is public (there is no
 * <code>ConfigAttributeDefinition</code> for the secure object invocation):
 * <ol type="a">
 * <li>As described above, the concrete subclass will be returned an
 * <code>InterceptorStatusToken</code> which is subsequently re-presented to
 * the <code>AbstractSecurityInterceptor</code> after the secure object has
 * been executed. The <code>AbstractSecurityInterceptor</code> will take no
 * further action when its {@link #afterInvocation(InterceptorStatusToken,
 * Object)} is called.</li>
 * </ol>
 * </li>
 * <li>Control again returns to the concrete subclass, along with the
 * <code>Object</code> that should be returned to the caller. The subclass
 * will then return that result or exception to the original caller.</li>
 * </ol>
 * </p>
 * 
 * @author Ben Alex
 * @version $Id: AbstractSecurityInterceptor.java 1790 2007-03-30 18:27:19Z
 * luke_t $
 */
public abstract class AbstractSecurityInterceptor implements InitializingBean, ApplicationEventPublisherAware,
		MessageSourceAware {
	// ~ Static fields/initializers
	// =====================================================================================

	protected static final Log logger = LogFactory.getLog(AbstractSecurityInterceptor.class);

	// ~ Instance fields
	// ================================================================================================

	private AccessDecisionManager accessDecisionManager;

	private AfterInvocationManager afterInvocationManager;

	private ApplicationEventPublisher eventPublisher;

	private AuthenticationManager authenticationManager;

	protected MessageSourceAccessor messages = AcegiMessageSource.getAccessor();

	private RunAsManager runAsManager = new NullRunAsManager();

	private boolean alwaysReauthenticate = false;

	private boolean rejectPublicInvocations = false;

	private boolean validateConfigAttributes = true;

	// ~ Methods
	// ========================================================================================================

	/**
	 * Completes the work of the <code>AbstractSecurityInterceptor</code>
	 * after the secure object invocation has been complete
	 * 
	 * @param token as returned by the {@link #beforeInvocation(Object)}}
	 * method
	 * @param returnedObject any object returned from the secure object
	 * invocation (may be<code>null</code>)
	 * 
	 * @return the object the secure object invocation should ultimately return
	 * to its caller (may be <code>null</code>)
	 */
	protected Object afterInvocation(InterceptorStatusToken token, Object returnedObject) {
		if (token == null) {
			// public object
			return returnedObject;
		}

		if (token.isContextHolderRefreshRequired()) {
			if (logger.isDebugEnabled()) {
				logger.debug("Reverting to original Authentication: " + token.getAuthentication().toString());
			}

			SecurityContextHolder.getContext().setAuthentication(token.getAuthentication());
		}

		if (afterInvocationManager != null) {
			// Attempt after invocation handling
			try {
				returnedObject = afterInvocationManager.decide(token.getAuthentication(), token.getSecureObject(),
						token.getAttr(), returnedObject);
			}
			catch (AccessDeniedException accessDeniedException) {
				AuthorizationFailureEvent event = new AuthorizationFailureEvent(token.getSecureObject(), token
						.getAttr(), token.getAuthentication(), accessDeniedException);
				publishEvent(event);

				throw accessDeniedException;
			}
		}

		return returnedObject;
	}

	public void afterPropertiesSet() throws Exception {
		Assert.notNull(getSecureObjectClass(), "Subclass must provide a non-null response to getSecureObjectClass()");

		Assert.notNull(this.messages, "A message source must be set");

		Assert.notNull(this.authenticationManager, "An AuthenticationManager is required");

		Assert.notNull(this.accessDecisionManager, "An AccessDecisionManager is required");

		Assert.notNull(this.runAsManager, "A RunAsManager is required");

		Assert.notNull(this.obtainObjectDefinitionSource(), "An ObjectDefinitionSource is required");

		Assert.isTrue(this.obtainObjectDefinitionSource().supports(getSecureObjectClass()),
				"ObjectDefinitionSource does not support secure object class: " + getSecureObjectClass());

		Assert.isTrue(this.runAsManager.supports(getSecureObjectClass()),
				"RunAsManager does not support secure object class: " + getSecureObjectClass());

		Assert.isTrue(this.accessDecisionManager.supports(getSecureObjectClass()),
				"AccessDecisionManager does not support secure object class: " + getSecureObjectClass());

		if (this.afterInvocationManager != null) {
			Assert.isTrue(this.afterInvocationManager.supports(getSecureObjectClass()),
					"AfterInvocationManager does not support secure object class: " + getSecureObjectClass());
		}

		if (this.validateConfigAttributes) {
			Iterator iter = this.obtainObjectDefinitionSource().getConfigAttributeDefinitions();

			if (iter == null) {
				logger.warn("Could not validate configuration attributes as the MethodDefinitionSource did not return "
						+ "a ConfigAttributeDefinition Iterator");
				return;
			}

			Set unsupportedAttrs = new HashSet();

			while (iter.hasNext()) {
				ConfigAttributeDefinition def = (ConfigAttributeDefinition) iter.next();
				Iterator attributes = def.getConfigAttributes();

				while (attributes.hasNext()) {
					ConfigAttribute attr = (ConfigAttribute) attributes.next();

					if (!this.runAsManager.supports(attr) && !this.accessDecisionManager.supports(attr)
							&& ((this.afterInvocationManager == null) || !this.afterInvocationManager.supports(attr))) {
						unsupportedAttrs.add(attr);
					}
				}
			}

			if (unsupportedAttrs.size() != 0) {
				throw new IllegalArgumentException("Unsupported configuration attributes: " + unsupportedAttrs);
			}

			logger.info("Validated configuration attributes");
		}
	}

	protected InterceptorStatusToken beforeInvocation(Object object) {
		Assert.notNull(object, "Object was null");

		if (!getSecureObjectClass().isAssignableFrom(object.getClass())) {
			throw new IllegalArgumentException("Security invocation attempted for object "
					+ object.getClass().getName()
					+ " but AbstractSecurityInterceptor only configured to support secure objects of type: "
					+ getSecureObjectClass());
		}

		ConfigAttributeDefinition attr = this.obtainObjectDefinitionSource().getAttributes(object);

		if (attr == null) {
			if (rejectPublicInvocations) {
				throw new IllegalArgumentException(
						"No public invocations are allowed via this AbstractSecurityInterceptor. "
								+ "This indicates a configuration error because the "
								+ "AbstractSecurityInterceptor.rejectPublicInvocations property is set to 'true'");
			}

			if (logger.isDebugEnabled()) {
				logger.debug("Public object - authentication not attempted");
			}

			publishEvent(new PublicInvocationEvent(object));

			return null; // no further work post-invocation
		}

		if (logger.isDebugEnabled()) {
			logger.debug("Secure object: " + object.toString() + "; ConfigAttributes: " + attr.toString());
		}

		if (SecurityContextHolder.getContext().getAuthentication() == null) {
			credentialsNotFound(messages.getMessage("AbstractSecurityInterceptor.authenticationNotFound",
					"An Authentication object was not found in the SecurityContext"), object, attr);
		}

		// Attempt authentication if not already authenticated, or user always
		// wants reauthentication
		Authentication authenticated;

		if (!SecurityContextHolder.getContext().getAuthentication().isAuthenticated() || alwaysReauthenticate) {
			try {
				authenticated = this.authenticationManager.authenticate(SecurityContextHolder.getContext()
						.getAuthentication());
			}
			catch (AuthenticationException authenticationException) {
				throw authenticationException;
			}

			// We don't authenticated.setAuthentication(true), because each
			// provider should do that
			if (logger.isDebugEnabled()) {
				logger.debug("Successfully Authenticated: " + authenticated.toString());
			}

			SecurityContextHolder.getContext().setAuthentication(authenticated);
		}
		else {
			authenticated = SecurityContextHolder.getContext().getAuthentication();

			if (logger.isDebugEnabled()) {
				logger.debug("Previously Authenticated: " + authenticated.toString());
			}
		}

		// Attempt authorization
		try {
			this.accessDecisionManager.decide(authenticated, object, attr);
		}
		catch (AccessDeniedException accessDeniedException) {
			AuthorizationFailureEvent event = new AuthorizationFailureEvent(object, attr, authenticated,
					accessDeniedException);
			publishEvent(event);

			throw accessDeniedException;
		}

		if (logger.isDebugEnabled()) {
			logger.debug("Authorization successful");
		}

		AuthorizedEvent event = new AuthorizedEvent(object, attr, authenticated);
		publishEvent(event);

		// Attempt to run as a different user
		Authentication runAs = this.runAsManager.buildRunAs(authenticated, object, attr);

		if (runAs == null) {
			if (logger.isDebugEnabled()) {
				logger.debug("RunAsManager did not change Authentication object");
			}

			// no further work post-invocation
			return new InterceptorStatusToken(authenticated, false, attr, object);
		}
		else {
			if (logger.isDebugEnabled()) {
				logger.debug("Switching to RunAs Authentication: " + runAs.toString());
			}

			SecurityContextHolder.getContext().setAuthentication(runAs);

			// revert to token.Authenticated post-invocation
			return new InterceptorStatusToken(authenticated, true, attr, object);
		}
	}

	/**
	 * Helper method which generates an exception containing the passed reason,
	 * and publishes an event to the application context.
	 * <p>
	 * Always throws an exception.
	 * </p>
	 * 
	 * @param reason to be provided in the exception detail
	 * @param secureObject that was being called
	 * @param configAttribs that were defined for the secureObject
	 */
	private void credentialsNotFound(String reason, Object secureObject, ConfigAttributeDefinition configAttribs) {
		AuthenticationCredentialsNotFoundException exception = new AuthenticationCredentialsNotFoundException(reason);

		AuthenticationCredentialsNotFoundEvent event = new AuthenticationCredentialsNotFoundEvent(secureObject,
				configAttribs, exception);
		publishEvent(event);

		throw exception;
	}

	public AccessDecisionManager getAccessDecisionManager() {
		return accessDecisionManager;
	}

	public AfterInvocationManager getAfterInvocationManager() {
		return afterInvocationManager;
	}

	public AuthenticationManager getAuthenticationManager() {
		return this.authenticationManager;
	}

	public RunAsManager getRunAsManager() {
		return runAsManager;
	}

	/**
	 * Indicates the type of secure objects the subclass will be presenting to
	 * the abstract parent for processing. This is used to ensure collaborators
	 * wired to the <code>AbstractSecurityInterceptor</code> all support the
	 * indicated secure object class.
	 * 
	 * @return the type of secure object the subclass provides services for
	 */
	public abstract Class getSecureObjectClass();

	public boolean isAlwaysReauthenticate() {
		return alwaysReauthenticate;
	}

	public boolean isRejectPublicInvocations() {
		return rejectPublicInvocations;
	}

	public boolean isValidateConfigAttributes() {
		return validateConfigAttributes;
	}

	public abstract ObjectDefinitionSource obtainObjectDefinitionSource();

	public void setAccessDecisionManager(AccessDecisionManager accessDecisionManager) {
		this.accessDecisionManager = accessDecisionManager;
	}

	public void setAfterInvocationManager(AfterInvocationManager afterInvocationManager) {
		this.afterInvocationManager = afterInvocationManager;
	}

	/**
	 * Indicates whether the <code>AbstractSecurityInterceptor</code> should
	 * ignore the {@link Authentication#isAuthenticated()} property. Defaults to
	 * <code>false</code>, meaning by default the
	 * <code>Authentication.isAuthenticated()</code> property is trusted and
	 * re-authentication will not occur if the principal has already been
	 * authenticated.
	 * 
	 * @param alwaysReauthenticate <code>true</code> to force
	 * <code>AbstractSecurityInterceptor</code> to disregard the value of
	 * <code>Authentication.isAuthenticated()</code> and always
	 * re-authenticate the request (defaults to <code>false</code>).
	 */
	public void setAlwaysReauthenticate(boolean alwaysReauthenticate) {
		this.alwaysReauthenticate = alwaysReauthenticate;
	}

	public void setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher) {
		this.eventPublisher = applicationEventPublisher;
	}

	public void setAuthenticationManager(AuthenticationManager newManager) {
		this.authenticationManager = newManager;
	}

	public void setMessageSource(MessageSource messageSource) {
		this.messages = new MessageSourceAccessor(messageSource);
	}

	/**
	 * By rejecting public invocations (and setting this property to
	 * <code>true</code>), essentially you are ensuring that every secure
	 * object invocation advised by <code>AbstractSecurityInterceptor</code>
	 * has a configuration attribute defined. This is useful to ensure a "fail
	 * safe" mode where undeclared secure objects will be rejected and
	 * configuration omissions detected early. An
	 * <code>IllegalArgumentException</code> will be thrown by the
	 * <code>AbstractSecurityInterceptor</code> if you set this property to
	 * <code>true</code> and an attempt is made to invoke a secure object that
	 * has no configuration attributes.
	 * 
	 * @param rejectPublicInvocations set to <code>true</code> to reject
	 * invocations of secure objects that have no configuration attributes (by
	 * default it is <code>false</code> which treats undeclared secure objects
	 * as "public" or unauthorized)
	 */
	public void setRejectPublicInvocations(boolean rejectPublicInvocations) {
		this.rejectPublicInvocations = rejectPublicInvocations;
	}

	public void setRunAsManager(RunAsManager runAsManager) {
		this.runAsManager = runAsManager;
	}

	public void setValidateConfigAttributes(boolean validateConfigAttributes) {
		this.validateConfigAttributes = validateConfigAttributes;
	}

	private void publishEvent(ApplicationEvent event) {
		if (this.eventPublisher != null) {
			this.eventPublisher.publishEvent(event);
		}
	}
}
